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MECHANICAL SPECIFICATIONS Rooftop Dedicated Outdoor Air Systems (DOAS)
Rooftop Dedicated Outdoor Air Systems (DOAS) Casing
Materials: Formed, 2-inch double wall closed cell foam insulated metal panels and 2” double wall closed cell foam insulated metal door construction, fabricated to permit access to internal components for maintenance.
Outside casing: Minimum 22-gauge, galvanized (G90) steel meeting ASTM A653 for components that do not receive a painted finish. Unit’s exterior shall be supplied from the manufacturer using G60 galvanneal steel with proprietary pre-painted material in the following PermatectorTM finish color; Concrete Gray-RAL 7023. This has been subjected to a salt spray test per ASTM-B117 and evaluated using ASTM-D714 and ASTM-D610 showing no observable signs of rust or blistering until reaching 2,500 hours.
o Optional Hi-Pro Poly Finish: Unit’s exterior shall be supplied from the manufacturer using G60 galvanneal steel with a high performance proprietary coating that has been subjected to a salt spray test per ASTM-B117 and evaluated using ASTM-D714 and ASTM-D610 showing no observable signs of rust or blistering until reaching 5,000 hours
Internal assemblies: Minimum 24-gauge, galvanized (G90) steel, except for motor supports which shall be minimum 14-gauge galvanized (G90) steel.
Cabinet Insulation: Comply with NFPA 90A and NFPA 90B and erosion requirements of UL 181.
Materials: Rigid urethane injected foam. o Thickness: 2 inch (50.8 mm) o Thermal Resistance: R13 o Meets UL94HF-1 flame requirements. o Location and application: Full coverage of entire exterior to include walls, roof of unit, unit base and doors.
Access panels / doors: Unit shall be equipped with insulated, hinged doors or removable access panels to provide easy access to all major components. Doors and access panels shall be fabricated of minimum 22-gauge galvanized G90 steel or painted galvannealed steel with 2-inch closed cell foam insulation.
Supply Air blower assemblies: Blower assembly shall consist of an electric motor and direct-drive fan(s). Assembly shall be mounted on heavy gauge galvanized steel rails and further mounted on 1.125 inch thick neoprene vibration isolators. Blower motor(s) shall be capable of continuous speed modulation and controlled by a VFD.
Exhaust Air blower assemblies: Blower assembly shall consist of an electric motor, with an ODP enclosure and a direct-drive fan. Assembly shall be mounted on heavy gauge galvanized steel rails and further mounted on 1.125 inch thick neoprene vibration isolators. Blower motor shall be capable of continuous speed modulation and controlled by a VFD.
Evaporator Coil: Evaporator coil shall be AHRI Certified and shall be (silver) soldered or brazed into the compressed refrigerant system. Coil shall be constructed of copper tubing, permanently bonded to aluminum fins and enclosed in a galvanized steel frame. If two compressors are used as components of the unit, then the evaporator coil shall be of “interlaced” configuration, permitting independent operation of either compressor without conflict with the other compressor.
o Optional: The evaporator and condenser coils are coated with ElectroFin® coil coating, E-Coat coated coils are tested and passed ASTM B-117 Salt Spray tests exceeding 10,000 hours.
Control panel / connections: Rooftop Ventilator units shall have an electrical control center where all high and low voltage connections are made. Control center shall be constructed to permit single-point high voltage power supply connections. RTU shall be equipped with a Unit Disconnect Switch. Electric heater shall have a separate electrical control center and separate high voltage power circuit as shown on the plans.
o optional: Electric heater shall have single point power
Condensate drain pan: Drain Pan shall be an integral part of the unit whenever a cooling option is included. Pan shall be formed of welded austenitic stainless-steel sheet material and provided with a drain connection at the front (access side) for connection to a P trap. Drain pan shall be sloped in two directions to provide positive draining and drain connector shall be sealed at penetration through cabinet wall.
P trap: If the unit is equipped with a condensate drain pan, contractor shall provide, or fabricate, and install an appropriate P trap, in accordance with all local and area codes and Best Practices.
Energy wheel: Unit energy wheel shall handle the full volume of outdoor and exhaust air without an energy wheel bypass damper(s). Energy wheel shall be of total enthalpy, rotary air-to-air type and shall be an element of a removable energy wheel cassette. The cassette shall consist of a galvanized steel framework (designed to produce laminar air flow through the wheel), an energy wheel as specified and a motor and drive assembly. The cassette shall incorporate a pre-tensioned urethane drive belt or a link-style belt with a five year warranty. The wheel media shall be a polymer film matrix. Wheel shall be comprised of individual segments that are removable for servicing. Silica gel desiccant shall be permanently bonded to the polymer film. The energy wheel is to have a five year warranty. Performance criteria are to be as specified in AHRI Standard 1060, complying with the Combined Efficiency data in the submittal.
Wheel Frost Control: Modulating Wheel shall be provided for frost control of the energy wheel. Control system shall include an outdoor air thermostat, and pressure sensor on the wheel assembly to initiate frost control sequence. Optional energy wheel VFD will modulate the wheel speed based on exhaust air leaving air temperature.
Optional: Chilled water, Hot water, Chilled water and hot water coil(s) shall be factory installed and meet the design requirements as above.
o Optional: Coil(s) shall be coated with ElectroFin® coil coating.
Reheat Coil with factory installed modulating hot gas reheat valve. o Optional: This coil is coated with ElectroFin® coil coating.
Optional Electric Post-heater: Post-heater shall be SCR control and shall include a temperature sensor with field adjustable set point, located in the outdoor air stream. Heat output of the post-heater shall be infinitely variable
Indirect gas furnace: o Shall be ETL Certified as a component of the unit. o Shall have an integral combustion gas blower. o Shall be ETL Certified for installation downstream of a cooling coil. o Shall have fault sensors to provide fault conditions to optional digital controller or building controls. o Shall have 4-pass tubular heat exchangers, constructed of type 409 stainless steel. Heat exchanger tubes
shall be installed on the vest. Heat exchanger tubes shall be supported and also permit expansion and contraction of the tubes].
o Heat exchanger shall have a twenty-five year extended warranty. o Furnace control shall be 4:1 Modulating.
Optional:10:1 Modulating, 12:1 Modulating, 13:1 Modulating, 14:1 Modulating,16:1 Modulating o Shall be encased in a weather-tight metal housing with intake air vents. Large, metal door shall provide easy
access to the enclosed vest plate, control circuitry, gas train, burner assembly, and exhaust blower. o Shall have solid state controls permitting stand-alone operation or control by building controllers.
Packaged DX System: Unit shall have an integral compressor(s) and evaporator coil located within the weather-tight unit housing.
o Optional: The evaporator and condenser coils are coated with ElectroFin® coil coating. o Condenser coils and appurtenant condenser fan assemblies shall be factory installed as integral
subassemblies of the unit and mounted on the exterior of the unit. Unit condenser fans shall feature swept owlet blade design resulting in reduced sound levels. Condenser fan motors shall be three phase, external rotor, type 56 frame, open air over and shaft up. Each condenser fan motor shall have a vented frame, rated for continuous duty and be equipped with an automatic reset thermal protector.
o Optional: Lead condenser fan will have an electronically commutated (EC) motor that will modulate to maintain a head pressure set point.
o Motors shall be UL Recognized and CSA Certified. The refrigerant compressor(s) shall be digital. o Optional: inverter hermetic scroll-type and shall be equipped with liquid line filter drier, thermostatic (optional:
electronic) expansion valves (TXV) (EXV)(s), manual reset high pressure and low pressure cutouts and all appurtenant sensors, service ports and safety devices. Compressed refrigerant system shall be fully charged with R-410A refrigerant. Each non-inverter scroll compressor shall be factory-equipped with an electric crankcase heater to boil off liquid refrigerant from the oil.
Packaged DX Control and Diagnostics: The Packaged DX system shall be controlled by an onboard digital controller (DDC) that indicates both owner-supplied settings and fault conditions that may occur. The DDC shall be programmed to indicate the following faults:
o Global alarm condition (active when there is at least one alarm) o Supply Air Proving alarm o Dirty Filter alarm o Compressor Trip alarm o Compressor Locked Out alarm o Supply Air Temperature Low Limit alarm
Sensor #1 Out of Range (outside air temperature) Sensor #2 Out of Range (supply air temperature)
Sensor #3 Out of Range (cold coil leaving air temperature)
Phase and brownout protection: RTU shall have a factory-installed phase monitor to detect electric supply phase loss and voltage brown-out conditions. Upon detection of a fault, the monitor shall disconnect supply voltage to all motors.
Motorized dampers / Outdoor Air / Return Air: Damper shall be of (optional: insulated) low leakage AMCA Class 1A certified construction. Leakage rate shall not exceed 3 CFM/ft2 @ 1 in. wg. and shall be factory installed.
AMCA Class 1A motorized recirculating air damper designed to permit 100% maximum recirculation of return air shall be factory installed.
Sensors are considered to be part of various optional operational modes or device controllers and are to be factory supplied and installed as specified by the A/E.
Curb Assembly: A curb assembly made of 14 gauge galvanized steel shall be provided by the factory for assembly and installation as part of this division. The curb assembly shall provide perimeter support of the entire unit and shall have duct adapter(s) for supply air and return air. Curb assembly shall enclose the underside of the unit and shall be sized to fit into a recess in the bottom of the unit. Contractor shall be responsible for coordinating with roofing contractor to ensure curb unit is properly flashed to provide protection against weather/moisture penetration. Contractor shall provide and install appropriate insulation for the curb assembly. The curb shall be the height of (14”, 18”, 24”, 36”).
Optional Service receptacle: 120 VAC GFCI service outlet shall be factory-provided and installed by this contractor in a location designated by the A/E. Unit contains a 120 VAC transformer to provide power to service outlet.
Optional Hail guards: Protects the condensing unit from damage due to extreme weather conditions such as hail and flying debris.
Optional Vapor Tight Lights: Provide service lights mounted in the unit to be used during times of routine maintenance. The lights must be wired by others on the jobsite as they will not be wired through the unit control center.
Optional 24V/120V Smoke detector – Duct smoke detector is shipped loose for field mounting and wiring in the supply or return air duct. The air duct smoke detector housing shall be UL listed per UL 268A specifically for use in air handling systems. The air duct smoke detector housing shall be suitable for mounting indoors. The detector shall operate at air velocities of 100 feet per minute to 4000 feet per minute (0.5 to 20.32 meters/second). The power supply voltage shall be 20-29 VDC, 24 VAC 50-60 Hz, and 120 VAC 50-60 Hz. The detector shall consist of an alarm initiation contact & two DPDT auxiliary contact closures.
a. Duct smoke detectors are neither a substitute for open area smoke detectors, for early warning detection, nor a replacement for a building’s regular fire detection system. Refer to NFPA 72 and 90A for additional information.
Blower Blower section construction Supply Air: direct drive motor(s) and blower(s) shall be assembled on a 14-gauge
galvanized steel platform and shall be equipped with 1.125 inch thick neoprene vibration isolation devices.
Blower assemblies: Shall be statically and dynamically balanced and designed for continuous operation at maximum rated fan speed and horsepower.
Fan: Direct drive, airfoil plenum fan with painted steel or aluminum wheels statically and dynamically balanced and AMCA certified for air and sound performance.
Blower section motor source quality control: Blower performance shall be factory tested for flow rate, pressure, power, air density, rotation speed and efficiency. Ratings are to be established in accordance with AMCA 210, “Laboratory Methods of Testing Fans for Rating.”
Motors
General: Blower motors greater than ¾ horsepower shall be “NEMA Premium™” unless otherwise indicated. Compliance with EPAct minimum energy-efficiency standards for single speed ODP and TE enclosures is not acceptable. Motors shall be heavy-duty, permanently lubricated type to match the fan load and furnished at the specified voltage, phase and enclosure. Motors shall be 60 cycle, 3 phase 208 / 230 / 460 volts. The designation “NEMA Premium™” applies to electric motors with efficiencies that are “better than EPAct.” The terms “high efficiency” or “premium efficiency” have no industry definitions.
Unit Controls The unit shall be constructed so that it can function as a stand-alone heating and cooling system controlled by factory-
supplied controllers, thermostats and sensors, or it can be operated as a heating and cooling system controlled by a Building Management System (BMS). This unit shall be controlled by a factory-installed microprocessor programmable controller (DDC) that is connected to various optional sensors.
Optional: Unit shall incorporate a DDC controller with integral LCD screen that provides text readouts of status. DDC controller shall have a built-in keypad to permit operator to access read-out screens without the use of ancillary
equipment, devices or software. DDC controllers that require the use of equipment or software that is not factory-installed in the unit are not acceptable. Alarm readouts consisting of flashing light codes are not acceptable.
RTU supply fan shall be configured for Constant Volume (ON / OFF) o Optional: network control, CO2 sensor by factory, duct pressure by factory, 0 – 10 VDC by others to DDC,
Single Zone VAV.
Exhaust fan shall be configured for Constant Volume (ON /OFF) o Optional: network control, building pressure by factory, damper tracking, 0-10 VCD by others to DDC, Supply
Tracking.
Outside Air / Return Air damper control shall be field adjustable two-position, Optional: network control, CO2 sensor by factory.
Optional: Economizer control shall be temperature, temperature/dew point, comparative temperature, comparative enthalpy.
Optional: Dirty filter sensor shall be factory-installed.
Operating protocol: The DDC shall be factory-programmed for Modbus, Modbus RTU, Modbus IP. o Optional: LonWorks, BACnet MSTP, BACnet IP
Variable Frequency Drive (VFD) [unit shall have factory installed variable frequency drive for modulation of the supply air blower assembly and exhaust air blower assembly. The VFD shall be factory-programmed for unit-specific requirements and shall not require additional field programming to operate.
Optional: Airflow monitoring required through thermistor or low-pressure transducer in the Outdoor/Exhaust/Supply/All airstreams.
Optional: Room thermostat shall be provided as a shipped loose item. The room thermostat shall have an LCD display to adjust the room temperature set-point from within the space. Room thermostat and room humidity sensor shall be provided as a shipped loose item.
Controller shall auto trend 7 days of operating points for trouble shooting purposes.
Embedded web page with complete web user interface to allow full remote control and monitoring of unit.
Alarm Recording: Controller shall store all alarm events for download.
Alarm Operating Snapshot: Controller shall store operating inputs and outputs at time of alarm.
Filters
Unit shall have supply final air filter shall be of 2 inch MERV 8 o Optional: hood filter shall be of 1 inch aluminum type o Optional: 4 inch MERV 8, MERV 13 with a 2 inch MERV 8 pre-filter, MERV 13, MERV 14 disposable pleated
type. o Energy recovery section shall have outdoor air and exhaust air filters of 2 inch MERV 8
Features and Benefits Rooftop Dedicated Outdoor Air System (DOAS) units provide 100% outdoor air in heating, cooling and dehumidification modes. Working with LG VRF systems, the LG Rooftop DOAS unit provides a complementary system solution to condition code-required outdoor air.
Airflow range from 500 CFM to 18,000 CFM
Tonnage from three (3) tons to seventy (70) tons
Down discharge or side discharge duct connections
Available in 208, 230, or 460 Volt / 3 phase power
Double wall casing with foam injection
Gas heat with 4:1 turndown
Four (4) to six (6) row direct expansion (DX) cooling coil
Modulating hot gas reheat coil for dehumidification mode
Variable capacity digital or inverter scroll compressor(s)
Direct drive supply fan with variable-frequency drive (VFD)
Microprocessor controller connectible to AC Smart or ACP central controllers (or stand-alone operation)
BACnet IP, BACnet MSTP, Modbus RTU, and Modbus IP protocols (BACnet® is a trademark of ASHRAE)
Web access to controller
2” MERV 8 supply-air filters (standard)
Discharge air control sequence with field mounted duct temperature sensor
Flexible design to match local design outdoor temperatures
Adjustable DX cooling coil discharge air set-point temperatures and unit discharge air temperatures
Dehumidification mode is triggered based on adjustable outdoor air dew point temperature set-points
Extensive end of line testing at factory
Insulated floor pan
Bottom return or side return duct connections for AR-DE models
Direct drive exhaust fan with VFD for AR-DE models
Phase voltage monitor
Options
Energy recovery wheel with rotation sensor (optional for AR-DE models)
Corrosion resistance coating for DX cooling reheat, condenser coils, and casing
High turndown (up to 16:1) gas heat control
Electric heat with silicon-controlled rectifier (SCR) control
Curbs (14”, 18”, 24”, high)
Hail guards
Airflow monitoring intake damper
VFD option for energy recovery wheel defrost control
4” MERV 8, 13, or 14 filters
Convenience outlet
Lonworks control protocol
(LonWorks® is a trademark of Echlelon Corporation.)
Capacity Data above may change if entering air temperatures, leaving air temperatures (LAT), or airflow rates are varied. Take appropriate actions at the end of HVAC equipment life to recover, recycle, reclaim or destroy R410A refrigerant according to
applicable regulations (40 CFR Part 82, Subpart F) under section 608 of CAA.
Capacity Data above may change if entering air temperatures, leaving air temperatures (LAT), or airflow rates are varied. Take appropriate actions at the end of HVAC equipment life to recover, recycle, reclaim or destroy R410A refrigerant according to
applicable regulations (40 CFR Part 82, Subpart F) under section 608 of CAA.